188 THE GEOLOGICAL AGE OF CENTEAL AND WEST CORNWALL. 



moderate depth. Tlie dark, carbonaceous or anthracitic* 

 schists raised from AVheal Jane, the Perran Mines, the 

 parishes of Illogan and Eedruth and many other localities, 

 exactly resemble the Longmynd rocks in the neighbourhood of 

 the Stiper Stones, as described by Murchison, whose words are 

 as follows: — "The lowest strata of the Longmynd, or those 

 forming the base of their eastern escarpment, range along the 

 western side of the Stretton Valley; they are thin, fragile, 



glossy schists, or clay-slate quartz veins occur here and 



there, but on the whole these strata consist chiefly of sandstone 

 rock both schistose and gritty, and often finely laminated, in 

 which the lines of deposit and even the rippled surfaces of the 

 beds are distinctly visible, the mass being but slightly affected 



by slaty cleavage some of the altered rocks contain 



copper veins, and others have cavities lined with crystals of 



c[uartz and occasionally with bitumen or mineral pitch 



the geologist will naturally attach much interest to the occurrence 



of flakes of anthracite in these very ancient strata for if 



these substances were formed out of vegetable or animal matter, 

 we can refer to little else than seaweeds or annelides as their 

 sources (" Siluria,^^ bth Ed., pp. 25-27.) 



The subterranean extension of these Pre-Silurian rocks is 

 indicated by many of the observations made by Mr. Henwood — 

 the more so as they were entirely unconnected with any theory. 

 Naturally a few irregularities occur in observations made near 

 fissure-lodes at different levels, but the following notes have 

 much meaning : — 



-i= f Wheal Eerland, Gwinear, soft light-coloured schists, ") Dip mostly 

 '^ •§ I Binner Downs, Crowan, blue schists, > W. of N. 20° — 40° 



■sj I W. Strawberry, „ „ J A few E. of S. 



I^S J Carsize Consols, „ silky deep blue schists, W. of N. 8° — 18° 

 g g ] Trevaskua, Gwinear, Hornblende schists, "^ 

 •g I I Relistian, „ deep blue schist, f Dip mostly 



O o I Providence, ,, blue schists, iW. of N. from 8° — 34° 



O l^Duffield, „ dark schist, J 



■ fGodolphin, Breage, blue schists 



to.S G-i- Work, „ deep bluish grey schists i t^. ,, ,, ^ 



iS-<W Vor 1 ' ,.x . ( Dip mostly N.E., 



p-- I Poladras, .' j '^^ ^^^^ schists, steep > occasionally S.W. 



[_H, Trannack, Sithney, dark schists, steep 1 



*We have repeatedly found thin scales of anthracite in the deep-seated rocks 

 of the localities referred to, and in many othei-s. 



